What initial action should a pilot take prior to entering Class C airspace?

Prior to entering Class C airspace, the appropriate initial action for a pilot is to contact approach control on the appropriate frequency. This process is crucial because Class C airspace is designed to provide a higher level of air traffic control service and requires pilots to establish two-way communication with the controlling facility before entry.

By contacting approach control, the pilot ensures they are receiving traffic advisories and that their intentions are understood by the air traffic control (ATC) personnel. This communication is essential for maintaining safety and efficiency in a busy airspace environment. Approach control will typically provide a clearance or instructions for entering the airspace, which are necessary for the pilot to follow to proceed safely.

In contrast, notifying ground control or requesting clearance from the tower pertains to airport operations and is more relevant during taxiing or take-off phases. Switching to a VFR navigation frequency is not the primary action for entering controlled airspace, as it does not establish the necessary communication with ATC. Thus, contacting approach control accurately reflects the standard procedure for engaging with the air traffic control system when entering Class C airspace.